The MuShield Advantage
Cryoperm – Cryogenic Magnetic Shielding
Often times, we receive requests to fabricate magnetic shields to be used at cryogenic temperatures (4.2k). Standard high permeability materials mumetal and HyMu 80 (specs ASTM A753 Alloy Type 4, and MIL-N-14411 Composition 1) are meant to be used at room temperature, so their maximum permeability will degrade and the magnetic shields will saturate as the application reaches cryogenic temperatures. Fortunately, a material called Cryoperm was developed to withstand the extreme cold or cryogenic temperatures.
Like mumetal, Cryoperm is a high permeability material made up of mostly nickel and requires post fabrication heat treatment to ensure maximum magnetic permeability. In order for the material to work as a magnetic shield in the cryogenic temperatures, metallurgists slightly altered the chemical composition to decrease the amount of nickel and molybdenum and introduced copper into the material’s recipe when compared to mumetal (ASTM A753 Alloy Type 4 and or MIL-N-14411 Composition 1). Also, the magnetic shields made from Cryoperm are put through a far more extensive heat treat cycle than mumetal. These changes to the material recipe and heat treat cycle ensure that your SQUID or Dewar’s magnetic shield will operate as expected at cryogenic temperatures.
MuShield offers Cryoperm in .020″ (.5mm) and .040″ (1mm) thicknesses, and has extensive history fabricating and heat treating magnetic shielding with this material.